Andrew Katz

Transport properties of high-Tc planar Josephson junctions fabricated by nanolithography and ion implantation

We have developed a process for fabrication of planar high-Tc Josephson junctions using nanolithography and a 200 keV ion implanter. Conduction occurs in the ab plane and has no metallurgical interface. Devices may be tuned to operate at temperatures between 1 K and the Tc of the undamaged superconducting material by varying the length of the weak link or by changing the amount of ion damage. We have examined the normal state and superconducting properties of these films and find behavior consistent with a de Gennes dirty limit proximity effect model. Current–voltage curves, Ic(T) and R(T) data suggest a temperature dependent superconducting-normal metal interface that we have incorporated into the proximity effect model.

Planar thin film YBa2Cu3O7−δ Josephson junctions via nanolithography and ion damage

We have developed a process to fabricate planar high-Tc Josephson junctions using nanolithography and a 200 keV ion implanter. Conduction occurs in the ab plane and is interface free. We can systematically tune devices to operate at temperatures between 1 K and the Tc of the undamaged superconducting material by varying the length of the weak link and by changing the amount of ion damage. All of the devices showed clear dc and ac Josephson effects. Measurement of R(T) and Ic(T) of the weak links revealed trends which were consistent with a proximity effect.

Fabrication of all thin‐film YBa2Cu3O7−δ /Pb Josephson tunnel junctions

All thin‐film YBCO/Pb Josephson tunnel junctions have been fabricated. The junctions showed a well‐defined Pb gap, Pb phonon structures, and very low leakage current. In addition, a higher bias spectroscopy revealed identical structures as have been seen in junctions made with single‐crystal YBCO. A thin uniform Ag diffusion barrier at the junction interface lowers the junction resistance enough to study the Josephson effct in YBCO/Pb tunnel junctions. Both the temperature and the magnetic field dependencies of the magnitude of the Josephson current displayed conventional behavior. The junctions were very reproducible and uniform as indicated by the Ic(B) pattern.

Interlayer conductivity in the superconductor Tl 2 Ba 2 CuO 6¿d : Energetics and energy scales

We report on infrared studies of the c-axis electrodynamics of

Stability and uniformity of planar high temperature Josephson junctions fabricated using nanolithography and ion damage

{\mathrm{Tl}}_{2}{\mathrm{Ba}}_{2}{\mathrm{CuO}}_{6+\ensuremath{\delta}}

Investigation of Nd-Ce-Cu-O planar tunnel junctions and bicrystal grain boundary junctions

crystals. A sum-rule analysis reveals spectral weight shifts that can be interpreted as a kinetic energy change at the superconducting transition. In optimally doped crystals, showing an incoherent normal-state response, the kinetic energy is lowered at

Josephson tunneling in high-{Tc} superconductors

Tl{T}_{c},

{ital c} -axis Josephson Tunneling between YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta} } and Pb: Direct Evidence for Mixed Order Parameter Symmetry in a High-{ital T}{sub {ital c}} Superconductor

but no significant change is found in the overdoped samples, which have more coherent conductivity at

Laterally disposed nanostructures of silicon on an insulating substrate

Tg{T}_{c}.